This invention generally relates to fluid valves and, more particularly, to frost-resistant water supply hydrants.
A frost-resistant sill cock or hydrant typically includes an elongated tubular body with a valve mechanism at a first end and with a spout and a valve operator at a second, opposing end. The elongated body allows the valve mechanism to be positioned in an environment where frost or freezing is not likely to Occur, such as inside a building or underground, while the spout and valve operator are positioned in a frost- or freezing-prone environment, commonly outside a building or otherwise out-of-doors. Typically, the operator is a handle, and an elongated actuator rod or stem extends within the tubular body between the handle and the valve, whereby manipulation of the handle moves the valve between open and closed positions. A predominant valve mechanism is what may be termed a "plunger valve," wherein a valve plunger or stopper is screw-actuated into and out of sealing engagement with a valve seat.
While the plunger valve provides a simple means for controlling flow from a water supply, it does not provide a truly positive control and is prone to damage during closing by over-tightening. That is, rather than screwing the valve plunger into a position of sealing engagement with the valve seat, a user will commonly forcibly close the valve, beyond the point of sealing, mashing and damaging valve seat and plunger sealing surfaces.
Further, plunger valves do not readily lend themselves to adaptation for accommodating contemporary health concerns, specifically back-flow prevention, sometimes known as anti-siphoning. Back-flow preventers or anti-siphon devices are desirable to prevent contamination of the water supply caused by siphoning a contaminant back through the hydrant and into the water supply. Plunger-type valves which incorporate an anti-siphon or back-flow prevention feature are commonly complicated with attendant reduced durability and added expense which often accompany complicated mechanisms. The durability of back-flow prevention and anti-siphon mechanisms may also be compromised by users who over-tighten valves upon closing.
Another feature found in contemporary valves is a vacuum breaker. The vacuum breaker will break the "vacuum" in a hydrant which enables siphoning fluid back through the hydrant to the water supply, thereby offering additional anti-siphon protection. The vacuum breaker also offers structural protection to the hydrant in the case of a careless user who leaves a hose connected to the spout or spigot so that the hydrant does not properly drain, but may freeze and rupture. In this instance, the vacuum breaker releases the "vacuum" which holds water in the hydrant in some circumstances, allowing such residual water to drain from the hydrant. The plunger valve does not readily lend itself to the vacuum breaker function which is commonly accomplished with a separate mechanism.
Thus, one will appreciate the need for a contemporary frost-resistant hydrant providing effective frost-resistance, back-flow prevention or anti-siphon protection, and integrated vacuum breaker protection without the use of conventional plunger valves.